Traffic Engineering (TE) is a technology that is concerned with performance optimization of networks. In general, Traffic Engineering includes a set of applications mechanisms, tools, and scientific principles that allow for measuring, modeling, characterizing and control of user data traffic in order to achieve specific performance objectives.
Multiprotocol label switching (MPLS) is a scheme in a high-performance telecommunication network which directs and carries data from one node to the next node in the network. In MPLS, labels are assigned to data packets. Packet forwarding decisions from one node to the next node in the network are made based on the contents of the label for each data packet, without the need to examine the data packet itself.
A circuit switched network usually includes multiple switch nodes (also referred to as “nodes”) which are arranged in a topology referred to in the art as a “shared mesh network.” Within the shared mesh network, user traffic can be transported between any two locations using predefined connections specifying particular links and/or switch nodes for conveying the user traffic.
The switch nodes are each provided with a control module. The control modules of the switch nodes function together to aid in the control and management of the circuit switched networks. The control modules can run a variety of protocols for conducting the control and management (Operation, Administration and Maintenance—referred to as OAM) of the circuit switched networks. One prominent protocol is referred to in the art as Generalized Multiprotocol Label Switching (GMPLS).
Generalized Multiprotocol Label Switching (GMPLS) is a type of protocol which extends multiprotocol label switching (MPLS) to encompass network schemes based upon time-division multiplexing (e.g. SONET/SDH, PDH, G.709), wavelength multiplexing, and spatial switching (e.g. incoming port or fiber to outgoing port or fiber). Multiplexing, such as time-division multiplexing is when two or more signals or bit streams are transferred over a common channel. In particular, time-division multiplexing (TDM) is a type of digital multiplexing in which two or more signals or bit streams are transferred as sub-channels in one communication channel, but are physically taking turns on the communication channel. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. After the last sub-channel, the cycle starts over again. Time-division multiplexing is commonly used for circuit mode communication with a fixed number of channels and constant bandwidth per channel. Time-division multiplexing differs from statistical multiplexing, such as packet switching, in that the timeslots are returned in a fixed order and preallocated to the channels, rather than scheduled on a packet by packet basis.
Generalized Multiprotocol Label Switching (GMPLS) includes multiple types of optical channel data unit (ODU) label switched paths (LSPs) including protection and recovery mechanisms which specify predefined (1) working connections within a shared mesh network having multiple nodes and communication links for transmitting data between a headend node and a tailend node; and (2) protecting connections specifying a different group of nodes and/or communication links for transmitting data between the headend node to the tailend node in the event that one or more of the working connections fail. A first node of a path is referred to as a headend node. A last node of a path is referred to as a tailend node. Data is initially transmitted over the optical channel data unit (ODU) Label Switched Path (LSP), referred to as the working connection, and then, when a working connection fails, the headend node or tailend node activates one of the protecting connections for redirecting data within the shared mesh network. Shared Mesh Protection (SMP) is a common protection and recovery mechanism in transport networks, where multiple paths can share the same set of network resources for protection purposes.
GMPLS protocols can be used for dynamic signaling to setup or teardown Optical channel Data Unit (ODUk/ODUj) connections, which may be known as working or protecting connections. These ODUk/ODUj connections are known as Sub-Network Connections (SNC). Sub-network connections are logical connections between two or more connected nodes and may be as small as a section between two nodes. A sub-network exists within a single layer and is typically a subsection of a larger network. The entire route a signal takes through a network from headend node to tailend node may be referred to as a path.
Current GMPLS mechanisms for setting up ODUk/ODUj Label Switched Path (LSP)/Sub-Network Connections (SNCs) are detailed, for example, in RFC3473 and RFC4328, and sub-network connections are further defined in ITU-T G.805.
Both a path and a sub-network connection can be monitored for alarm and/or error conditions. A tandem connection can be defined on a path or a sub-network connection for the purpose of monitoring for alarm and/or error conditions. This monitoring is known as Path Monitoring (PM) and Tandem Connection Monitoring (TCM). Monitoring can determine signal fail (SF) and signal degrade (SD) conditions. Monitoring can also be used for fault localization, protection, and/or restoration under failure conditions. Monitoring the characteristics of a connection or path may include, for example, determining capacity, ability, defects, errors, alarms, signal fail conditions, signal degrade conditions, fault localization, connection protection, and/or connection restoration. Other characteristics of the connection may be monitored as well.
Activation and deactivation of tandem connections requires a sequence of configuration steps at one or more nodes. Activation of monitoring in a node, for example—activation of a Tandem Connection Monitoring layer, creates an entity within the node. Tandem connections are further explained in ITU-T G.709, G.805, and G874.1.
Tandem Connection Monitoring utilizes fields within the data overhead transmitted on the data plane in an optical transport network (OTN). The optical transport hierarchy (OTH) supports the operation and management aspects of optical transport networks (OTN) of various architectures, e.g., point-to-point (linear), ring and mesh architectures. One part of the optical transport hierarchy is a multiplex hierarchy, which is a hierarchy consisting of an ordered repetition of tandem digital multiplexers that produce signals of successively higher data rates at each level of the hierarchy. An exemplary multiplexing hierarchy may be specified by way of optical channel data units, i.e., ODUj, where j varies from 0 to 4; and optical channel transport units, i.e., OTUk, where k varies from 1 to 4. The optical channel data units refer to a frame format for transmitting data which can be either fixed in the amount of data and data rate or variable in the amount of data and/or data rate.
Like all other ODUjs, the ODU0 frame format includes a structure of four rows and 3824 columns. The ODU0 frame format is further divided into an ODUk overhead area (the first fourteen columns) and an optical channel payload unit (OPU) area. The optical channel payload unit (OPU) area contains two columns of overhead and 3808 columns of payload area which is available for the mapping of client data.
The ODUk overhead area is comprised of multiple fields including six Tandem Connection Monitoring (TCMi) overhead fields (TCM1, TCM2, TCM3, TCM4, TCM5, and TCM6) and a Path Monitoring (PM) overhead field. Tandem Connection Monitoring and Path Monitoring fields can be used in Tandem Connection Monitoring and in Path Monitoring to monitor connections and paths within optical transport networks. One or more Tandem Connection Monitoring fields can be used for fault localization, fast Sub-Network Connection restoration, segment protection, and/or fast segment restoration ITU-T G.709 further defines TCM fields and PM fields and defines TCM overhead bytes for six layers of TCM per ODUk connection.
TCMi Fields
The six Tandem Connection Monitoring fields are dedicated to six levels of tandem connection monitoring per ODUk connection. The number of monitored connections along an ODUk trail may vary between zero and six. The monitored connections may be nested, cascaded, or both nested and cascaded, or overlapped. The TCMi fields are each three bytes long and each includes the following sub-fields: a Trail Trace Identifier (TTI) field, a Bit Interleaved Parity 8 (BIP-8) field, a Backward Defect Indication (BDI) field, a Backward Error Indication and Backward Incoming Alignment Error (BEI/BIAE) field, and a status bits field indicating the presence of TCM overhead, incoming alignment error, or maintenance signal (STAT).
The TTI field can transport a 64 byte TTI signal broken up over a number of ODUk frames. The TTI field includes the following sub-fields: a Source Access Point Identifier (SAPI) field, a Destination Access Point Identifier (DAPI) field, and a network Operator Specific field. The SAPI field identifies the tandem connection trail source point. The DAPI field identifies the expected tandem connection trail sink (i.e. the trail end point). Access Point Identifiers (APIs) are globally unique in the APIs' layer network. The set of all APIs belonging to a single administrative layer network form a single API scheme. However, the scheme of APIs for each administrative layer network can be independent from the scheme in any other administrative layer network. The APIs may be available to other network operators. APIs typically do not change while the access point remains in existence. Normally, the API can identify the country and network operator which is responsible for routing to and from the access point.
The BIP-8 field is a one-byte Error Detection Code (EDC) signal. The BIP-8 field provides a bit interleaved parity-8 code. The contents of BIP-8 field are computed over the bits in the OPUk area of the ODUk frame I, and inserted in the BIP-8 field (associated with the tandem connection monitoring level) in ODUk frame i+2. The BIP-8 field is further described in ITU-T G.707.
The single-bit BDI field can convey, towards the source, a signal fail status detected in a tandem connection termination sink function.
The BEI/BIAE field is a four bit field which can convey, towards the source (upstream), the count of interleaved-bit blocks that have been detected as being in error by the corresponding ODUk tandem connection monitoring sink using the BIP-8 field code. The BEI/BIAE field is also used to convey in the upstream direction an incoming alignment error (IAE) condition that is detected in the corresponding ODUk tandem connection monitoring sink in the IAE overhead.
The STAT field is a three bit status field. The STAT field can be used to indicate the presence of a maintenance signal, or if there is no source tandem connection monitoring end point active, or if there is an incoming alignment error at the source tandem connection monitoring end point.
PM Field
The ODUk overhead portion also includes the Path Monitoring (PM) field. The PM field has similar sub-fields as those described for the TCM fields. The PM field is used for monitoring the end-to-end connection through the network. The PM field is further described in ITU-T G.709.
PM&TCM Field
The ODUk overhead portion also includes the PM&TCM field. The PM&TCM field includes the following sub-fields: six ODUk TCM Delay Measurement (DMti) fields (DM1, DMt2, DMt3, DMt4, DMt5, and DMt6); a Path Delay Measurement (DMp) field; and a reserved (RES) field.
For ODUk tandem connection monitoring, the one-bit tandem connection Delay Measurement (DMti) signals are defined to convey the start of the delay measurement test.
For ODUk path monitoring, the one-bit Path Delay Measurement (DMp) signal is defined to convey the start of the delay measurement test.
The DMti fields, the DMp field, and the associated signals are further described in ITU-T G.798.
The ODUk Reserved Overhead (RES) fields contain eight bytes and one bit (where the one bit is located in a sub-field in the PM&TCM field) and are reserved for future standardization.
Currently, GMPLS mechanisms exist for setting up ODUk/ODUj label switched paths/sub-network connections. However, a node in a connection oriented network must be manually and individually configured in order to enable the node in an optical transport network to utilize the ODUk Tandem Connection Monitoring fields and Path Monitoring fields for monitoring the sub-network connections in the optical transport network. The node is manually configured at each port connected to the client. This manual configuration of the node typically takes place after a connection is established. Additionally, typically only the nodes at the beginning and the end of the connection (known as the head end and tail end nodes, respectively) are configured in this manner to monitor the connection in the optical transport network (OTN), although intermediate nodes can also be configured.
Once the node is configured to monitor paths and/or tandem connections, the node is adapted to utilize the data in the PM and TCM fields, as well as to input data into the PM and TCM fields.
However, there currently is not a method or system within GMPLS protocol for dynamic signaling configuration and setup of Tandem Connection Monitoring layers for ODUk/ODUj connections on Label Switched Paths (LSPs).